1. Field of the Invention
The present invention is directed to a fast multiplied harmonic signal generating device and so on. The present invention further relates to a fast multiplied harmonic signal generating method. Firstly, the one embodiment of the method suppresses even order components by adjusting bias voltage. Next, the method suppresses a 0th order component using a filter so as to obtain ±2nd order components. Finally, the method obtains 4th harmonic wave component the frequency of which is 4 times that of a modulating signal's. Further, the present invention relates to a fast multiplied harmonic signal generating method obtaining multiplied harmonic signal, including 6th harmonic wave component and 8th harmonic wave component, using similar principle as above. The present invention is further directed to an apparatus that can attain the above methods.
2. Description of the Related Art
Recently, various kinds of multiplied harmonic signal generating techniques were proposed. However such techniques have problem that it can not suppress unnecessary components.
For example, the method of obtaining 2nd harmonic component by means of optical phase modulator (see the following reference 1). This technique basically uses an optical filter to suppress unnecessary components. On the other hand, the optical filter does not have strict wavelength response. Thus, it was difficult to suppress unnecessary component without fading necessary component when the frequency of the unnecessary component and that of necessary component is close. Further the characteristic of the optical filter alters reflecting surrounding temperature. Thus, when the temperature alters, it become difficult to suppress unnecessary component and it sometimes fades necessary components.
[Reference 1] Proceedings of SPIE—Volume 5579 Photonics North 2004: Photonic Applications in Telecommunications, Sensors, Software, and Lasers, John C. Armitage, Roger A. Lessard, George A. Lampropoulos, Editors, November 2004, pp. 673-679